What kind of developmental potential is present in elementary schoolchildren but hindered by the traditional type of education? Half a century ago Daniel El'konin and Vasili Davydov, the leaders of Russian Vygotskian educational psychology started answering this question. They suggested that reflection is a basic human ability and it can be developed in younger students. Reflection includes thinking about one's own actions and thoughts, taking other people's point of view, and understanding oneself. In this paper I present results of the design experiments conducted in Russian schools that deliberately promote students' reflection. In these schools the majority of children achieve high levels of reflection previously attributed only to the gifted students. One aspect of reflection will be given special attention, the ability of the student to take the perspective of another person. The comparative microanalysis of learning discourse in the first and the fourth grades demonstrated a significant growth of this ability through the first three years of schooling and made evident limitations imposed by the existing structure of the classroom cooperation. The long-term effects of education based on the principles of learning activity are demonstrated on the basis of the recent PISA study data. (Contains 3 tables and 3 figures.)